In many commercial packaging applications it is desirable to provide multilayer packaging materials in order to produce a package having multiple attributes. For instance, in the food packaging area, it is especially desirable to make consumer packages which are readily opened by digital pull-apart force. Delamination seals are particularly useful for this purpose. These seals include two or more layers and in which delamination occurs between two of the layers. Such a delamination system works on the principal that a bond is formed between structural package layers and one of the layers making up the delamination structure which has a greater bond strength than the peelable bond between the two film layers which delaminate from each other with manual force. Choice of materials determines which layers will delaminate from each other.
It is also important to place perishable foods such as meats and cheeses into packages which allow for the preservation of these foods for as long as possible. Maximizing the time in which the food remains preserved, especially between initial packaging and arrival at the retail store is especially important. Atmospheric oxygen is a common culprit in promoting food spoilage. Oxygen is reduced to a variety of free radical species which oxidize carbon-carbon double bonds in food and other perishable products. Such oxidation by free radicals adversely affects the odor and flavor of certain foods and can affect the stability of non-food products. Thus, it is desirable to incorporate oxygen barrier film layers into packaging materials. A particularly effective oxygen barrier material is ethylene vinyl alcohol (EVOH).
Providing packages having multiple attributes such as an easy opening delamination seal and oxygen barrier properties frequently necessitates bonding multiple layers of film having different properties together. Unfortunately, many film materials are not compatible with and thus, do not adequately seal to other packaging materials. It has been especially difficult to directly seal oxygen barrier film layers containing EVOH to film layers typically used in delamination seal technology. One approach to the problem is to interpose extra layers in between the EVOH layer and the layers making up the delamination seal. However, this approach does not always prove expedient or convenient.
A need therefore exists for a multilayer packaging material having an oxygen barrier layer as well as delamination layers. Furthermore, it is desirable to achieve this structure with a minimal number of film layers. It is therefore necessary to find film layer materials which bind together well and also retain their independent attributes of ease of delamination and oxygen barrier properties.